1. The single cable connecting all devices in a bus topology. 2. The type of circuit used by a computer's motherboard to transmit data to components.
Andrews, Jean (2007). A+ Guide to Managing and Maintaining Your PC, Sixth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thompson Learning, Inc..
CPU
(Central Processing Unit) The computational control unit of a computer, the device that interprets and carries out instructions.
ean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Desktop
The initial screen that is displayed when an OS has a GUI interface loaded.
ean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Driver
A program that controls a device. Every device, whether it be a printer, disk drive, or keyboard, must have a driver program. Many drivers, such as the keyboard driver, come with the operating system. For other devices, you may need to load a new driver when you connect the device to your computer. In DOS systems, drivers are files with a.SYS extension. In Windows environments, drivers often have a.DRV extension. A driver acts like a translator between the device and programs that use the device. Each device has its own set of specialized commands that only its driver knows. In contrast, most programs access devices by using generic commands. The driver, therefore, accepts generic commands from a program and then translates them into specialized commands for the device.
Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. An IDE interface is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive.
Short for modulator-demodulator. A modem is a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms. Fortunately, there is one standard interface for connecting external modems to computers called RS-232. Consequently, any external modem can be attached to any computer that has an RS-232 port, which almost all personal computers have. There are also modems that come as an expansion board that you can insert into a vacant expansion slot. These are sometimes called onboard or internal modems. While the modem interfaces are standardized, a number of different protocols for formatting data to be transmitted over telephone lines exist. Some, like CCITT V.34, are official standards, while others have been developed by private companies. Most modems have built-in support for the more common protocols -- at slow data transmission speeds at least, most modems can communicate with each other. At high transmission speeds, however, the protocols are less standardized. Aside from the transmission protocols that they support, the following characteristics distinguish one modem from another: # bps : How fast the modem can transmit and receive data. At slow rates, modems are measured in terms of baud rates. The slowest rate is 300 baud (about 25 cps). At higher speeds, modems are measured in terms of bits per second (bps). The fastest modems run at 57,600 bps, although they can achieve even higher data transfer rates by compressing the data. Obviously, the faster the transmission rate, the faster you can send and receive data. Note, however, that you cannot receive data any faster than it is being sent. If, for example, the device sending data to your computer is sending it at 2,400 bps, you must receive it at 2,400 bps. It does not always pay, therefore, to have a very fast modem. In addition, some telephone lines are unable to transmit data reliably at very high rates. # voice/data: Many modems support a switch to change between voice and data modes. In data mode, the modem acts like a regular modem. In voice mode, the modem acts like a regular telephone. Modems that support a voice/data switch have a built-in loudspeaker and microphone for voice communication. # auto-answer : An auto-answer modem enables your computer to receive calls in your absence. This is only necessary if you are offering some type of computer service that people can call in to use. # data compression : Some modems perform data compression, which enables them to send data at faster rates. However, the modem at the receiving end must be able to decompress the data using the same compression technique. # flash memory : Some modems come with flash memory rather than conventional ROM, which means that the communications protocols can be easily updated if necessary. # Fax capability: Most modern modems are fax modems, which means that they can send and receive faxes. To get the most out of a modem, you should have a communications software package, a program that simplifies the task of transferring data.
(Network Interface Card)Often abbreviated as NIC, an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.
The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers. For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system. Operating systems can be classified as follows: # multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users. # multiprocessing : Supports running a program on more than one CPU. # multitasking : Allows more than one program to run concurrently. # multithreading : Allows different parts of a single program to run concurrently. # real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time. Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux. As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.
A self-contained operating environment that behaves as if it is a separate computer. For example, Java applets run in a Java virtual machine (VM) that has no access to the host operating system. This design has two advantages: * System Independence: A Java application will run the same in any Java VM, regardless of the hardware and software underlying the system. * Security: Because the VM has no contact with the operating system, there is little possibility of a Java program damaging other files or applications. The second advantage, however, has a downside. Because programs running in a VM are separate from the operating system, they cannot take advantage of special operating system features.
A table that the operating system uses to locate files on a disk. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. The FAT keeps track of all these pieces. In DOS systems, FATs are stored just after the boot sector. The FAT system for older versions of Windows 95 is called FAT16, and the one for new versions of Windows 95 and Windows 98 is called FAT32.
(1) Refers to the condition of a disk in which files are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use a disk frequently, creating, deleting, and modifying files. At some point, the operating system needs to store parts of a file in noncontiguous clusters. This is entirely invisible to users, but it can slow down the speed at which data is accessed because the disk drive must search through different parts of the disk to put together a single file. In DOS 6.0 and later systems, you can defragment a disk with the DEFRAG command. You can also buy software utilities, called disk optimizers or defragmenters, that defragment a disk. (2) Fragmentation can also refer to RAM that has small, unused holes scattered throughout it. This is called external fragmentation. With modern operating systems that use a paging scheme, a more common type of RAM fragmentation is internal fragmentation. This occurs when memory is allocated in frames and the frame size is larger than the amount of memory requested.
Also known as CD-RW. A CD drive that can record or write data to a CD. The data can be erased and overwritten. The drive may or may not be multisession.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Floppy drive
Also known as a floppy disk drive 1. Device that reads from and writes on a floppy disk. 2. A drive that can hold either a five and a quarter inch or three and one half floppy disk.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Hard drive
The main secondary storage device of a PC, a small case that contains magnetic coated platters that rotate at high speed.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
RAM
(Random Access Memory) Memory modules on the motherboard containing microchips used to temporarily hold data and programs while the CPU processes both. Information in RAM is lost when the PC is turned off.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
ROM
(Read-Only Memory) Chips that contain programming code and cannot be erased.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
DIMM
(Dual Inline Memory Module) A miniature circuit board installed on a motherboard to hold memory. DIMMs can hold up to 2 GB of RAM on a single module.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
SIMM
(Single Inline Memory Module) A miniature circuit board used in older computers to hold RAM. SIMMs hold 8, 16, 32, or 64 MB on a single module.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Virtual Memory
An imaginary memory area supported by some operating systems (for example, Windows but not DOS) in conjunction with the hardware. You can think of virtual memory as an alternate set of memory addresses. Programs use these virtual addresses rather than real addresses to store instructions and data. When the program is actually executed, the virtual addresses are converted into real memory addresses. The purpose of virtual memory is to enlarge the address space, the set of addresses a program can utilize. For example, virtual memory might contain twice as many addresses as main memory. A program using all of virtual memory, therefore, would not be able to fit in main memory all at once. Nevertheless, the computer could execute such a program by copying into main memory those portions of the program needed at any given point during execution. To facilitate copying virtual memory into real memory, the operating system divides virtual memory into pages, each of which contains a fixed number of addresses. Each page is stored on a disk until it is needed. When the page is needed, the operating system copies it from disk to main memory, translating the virtual addresses into real addresses. The process of translating virtual addresses into real addresses is called mapping. The copying of virtual pages from disk to main memory is known as paging or swapping.
Short for NT File System, one of the file system for the Windows NT operating system (Windows NT also supports the FAT file system). NTFS has features to improve reliability, such as transaction logs to help recover from disk failures. To control access to files, you can set permissions for directories and/or individual files. NTFS files are not accessible from other operating systems such as DOS. For large applications, NTFS supports spanning volumes, which means files and directories can be spread out across several physical disks.
Used typically in reference to a computer language to mean a command or statement in the language that is going to be made invalid or obsolete in future versions.
Short for World Wide Web Consortium, an international consortium of companies involved with the Internet and the Web. The W3C was founded in 1994 by Tim Berners-Lee, the original architect of the World Wide Web. The organization's purpose is to develop open standards so that the Web evolves in a single direction rather than being splintered among competing factions.
Labels that idetify and structure the different parts of a Web page. Some elements have one or more attributes, which further describe the purpose and content, if any, of the element.
The XML Validation (eXtensible Markup Language) let check a document in XML language if it is well formed and it is adjusted to a defined structure. A well formed document follows the basic rules of XML established for the design of documents. Moreover a valid document respects the rules dictated by a DTD or XML schema.
Short for document type definition. A DTD states what tags and attributes are used to describe content in an SGML, XML or HTML document, where each tag is allowed, and which tags can appear within other tags. For example, in a DTD one could say that LIST tags can contain ITEM tags, but ITEM tags cannot contain LIST tags. In some editors, when authors are inputting information, they can place tags only where the DTD allows. This ensures that all the documentation is formatted the same way. Applications will use a document's DTD to properly read and display a document's contents. Changes in the format of the document can be easily made by modifying the DTD.
(IEEE 1394) Standards for an expansion bus that can also be configured to work as a local bus. It is expected to replace the SCSI bus, providing an easy method to install and configure fast I/O devices. Also known as i.Link.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
IR
An invisible band of radiation at the lower end of the visible light spectrum. With wavelengths from 750 nm to 1 mm, infrared starts at the end of the microwave spectrum and ends at the beginning of visible light. Infrared transmission typically requires an unobstructed line of sight between transmitter and receiver. Widely used in most audio and video remote controls, infrared transmission is also used for wireless connections between computer devices.
(1) (Radio Frequency) Definition #2 below explains radio frequencies; however, the term may be used to contrast wireless transmission systems that do not require line of sight with those that do. For example, an RF remote control does not require line of sight to the device it is controlling. (2) (Radio Frequency) The range of electromagnetic frequencies above the audio range and below infrared light (from 10 kHz to 300 GHz). Except for infrared (IR) transmission, all wireless transmission uses RF, including AM and FM radio, TV, satellites, portable phones, cellphones and wireless networks. RF signals can be focused in one direction (directional), or they can transmit in all directions (omnidirectional).
An industry standard for serial communication connections. Adopted by the Electrical Industries Association (EIA), this recommended standard defines the specific lines and signal characteristics used by serial communications controllers to standardize the transmission of serial data between devices.
(2000). MCSE Training Kit Networking Essentials Plus, Third Edition. Redmond, Washington: Microsoft Press, A Division of Microsoft Corporation.
Serial
Relating to or being a connection in a computer system in which the bits of a byte are transmitted sequentially over a single wire.
(Small Computer System Interface) A fast interface between a host adapter and the CPU that can daisy chain as many as 7 to 15 devices on a single bus.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
USB
(Universal Serial Bus) A serial bus with a data transfer rate of 12 megabits per second (Mbps) for connecting peripherals to a microcomputer. USB can connect up to 127 peripheral devices to the system through a single, general-purpose port. This is accomplished by daisy chaining peripherals together. USB is designed to support the ability to automatically add and configure new devices and the ability to add such devices without having to shut down and restart the system.
(2000). MCSE Training Kit Networking Essentials Plus, Third Edition. Redmond, Washington: Microsoft Press, A Division of Microsoft Corporation.
ISP
Short for Internet Service Provider, a company that provides access to the Internet. For a monthly fee, the service provider gives you a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs). ISPs are also called IAPs (Internet Access Providers).
Short for Uniform Resource Identifier, the generic term for all types of names and addresses that refer to objects on the World Wide Web. A URL is one kind of URI.
(Uniform Resource Locator) Provides the hypertext links between documents on the World Wide Web (WWW). Every resource on the Internet has its own location identifier, or URL, that specifies the server to access as well as the access method and the location. URLs can use various protocols including FTP and HTTP.
(2000). MCSE Training Kit Networking Essentials Plus, Third Edition. Redmond, Washington: Microsoft Press, A Division of Microsoft Corporation.
Blog
Short for Web log, a blog is a Web page that serves as a publicly accessible personal journal for an individual. Typically updated daily, blogs often reflect the personality of the author.
Network neutrality or net neutrality, as it is abbreviated, is the term used to describe networks that are open to equal access to all . They are non-discriminatory as they do not favor any one destination or application over another. Due to the political debate in 2006, the definition of network neutrality has changed to mean those who run networks as opposed to the network itself, where net neutrality is generally understood to mean that the service and telecommunication providers do not discriminate against rivals or individuals when they charge fees or when they prioritize traffic. Net neutrality is a major issue as the U.S. considers new telecommunications laws. In a general sense, it is mainly supported by companies that provide services at the edge of the network, and is generally opposed by companies that manage the middle of the network.
A collaborative Web site comprises the perpetual collective work of many authors. Similar to a blog in structure and logic, a wiki allows anyone to edit, delete or modify content that has been placed on the Web site using a browser interface, including the work of previous authors. In contrast, a blog, typically authored by an individual, does not allow visitors to change the original posted material, only add comments to the original content. The term wiki refers to either the Web site or the software used to create the site.
Short for Concurrent Versions System, an open-source, network-transparent program that allows developers to keep track of different development versions of source code. CVS does not maintain multiple versions of source code files but keeps a single copy and records of all of the changes that are made. When a developer wants a particular development version of a file, CVS will reconstruct that version based on its records. Bugs can often get into code when it is modified and may not be detected until long after the modification is made. CVS can retrieve old versions of the code, allowing the developer to see precisely which change caused the bug. CVS is also useful when more than one person is working on a specific file, where it is possible for the developers to overwrite each other's changes. CVS solves this problem by having each developer work in an individual directory and then merging the work from each after the work is complete. It is important to note that CVS is not a build system but rather a way to control disparate versions of code as it is developed over time.
Often referred to simply as peer-to-peer, or abbreviated P2P, a type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-peer networks are generally simpler, but they usually do not offer the same performance under heavy loads.
Short for File Transfer Protocol, the protocol for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser and SMTP for transferring electronic mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer. FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).
A type of data transmission in which a single medium (wire) can carry several channels at once. Cable TV, for example, uses broadband transmission. In contrast, baseband transmission allows only one signal at a time. Most communications between computers, including the majority of local-area networks, use baseband communications. An exception is B-ISDN networks, which employ broadband transmission.
BitTorrent is a file distribution system used for transferring files across a network of people. As you download a file, BitTorrent places what you download on upload for other users; when multiple people are downloading the same file at the same time they upload pieces of the file to each other. BitTorrent pieces together the file you are downloading, to where the first part of a file you get may be the last part someone else gets. As you continue to retrieve the file, BitTorrent also uploads data to other users. For example, a person with 98 percent of the file done is directed to the people with the 2 percent of the file they still need. The files downloaded via BitTorrent are called torrents.
A computer or device on a network that manages network resources. For example, a file server is a computer and storage device dedicated to storing files. Any user on the network can store files on the server. queries. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks. On multiprocessing operating systems, however, a single computer can execute several programs at once. A server in this case could refer to the program that is managing resources rather than the entire computer.
A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN). Most LANs connect workstations and personal computers. Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions. There are many different types of LANs Ethernets being the most common for PCs. Most Apple Macintosh networks are based on Apple's AppleTalk network system, which is built into Macintosh computers. The following characteristics differentiate one LAN from another: # topology : The geometric arrangement of devices on the network. For example, devices can be arranged in a ring or in a straight line. # protocols : The rules and encoding specifications for sending data. The protocols also determine whether the network uses a peer-to-peer or client/server architecture. # media : Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves. LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.
A local-area network (LAN) architecture developed by Xerox Corporation in cooperation with DEC and Intel in 1976. Ethernet uses a bus or star topology and supports data transfer rates of 10 Mbps. The Ethernet specification served as the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. Ethernet uses the CSMA/CD access method to handle simultaneous demands. It is one of the most widely implemented LAN standards. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. And the newest version, Gigabit Ethernet supports data rates of 1 gigabit (1,000 megabits) per second.
National Lambda Rail is a high-speed national computer network in the United States that runs over fiber-optic lines, and is the first transcontinental Ethernet network. The name is shared by the organization of research institutions that developed the network, and, to date, plans to continue developing it. LambdaRail is similar to the Abilene Network, but LambdaRail permits deeper experimentation than Abilene does. It is primarily oriented to aid terascale computing efforts, but is also not intended to be a service network, but to be used as a network testbed for experimentation with next-generation large-scale networks. National LambdaRail is a university-based and -owned initiative, in contrast with Abilene and Internet2, which are university-corporate sponsorships. This gives universities more control to use the network for these research projects. Links in the network use dense wavelength-division multiplexing (DWDM), which allows up to 32 or 40 individual optical wavelengths to be used (depending on hardware configuration at each end). At present, individual wavelengths are used to carry a 10-gigabit Ethernet signal, although other systems such as SONET may also be used in the future.
An agreed-upon format for transmitting data between two devices. The protocol determines the following: # the type of error checking to be used * data compression method, if any # how the sending device will indicate that it has finished sending a message * how the receiving device will indicate that it has received a message. There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster. From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers. The protocol can be implemented either in hardware or in software.
Abbreviation of Transmission Control Protocol, and pronounced as separate letters. TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.
A network architecture in which each computer or process on the network is either a client or a server. Servers are powerful computers or processes dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network servers ). Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power. Another type of network architecture is known as a peer-to-peer architecture because each node has equivalent responsibilities. Both client/server and peer-to-peer architectures are widely used, and each has unique advantages anddisadvantages. Client-server architectures are sometimes called two-tier architectures.
A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets. A passive hub serves simply as a conduit for the data, enabling it to go from one device (or segment) to another. So-called intelligent hubs include additional features that enables an administrator to monitor the traffic passing through the hub and to configure each port in the hub. Intelligent hubs are also called manageable hubs. A third type of hub, called a switching hub, actually reads the destination address of each packet and then forwards the packet to the correct port.
A device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network. Routers are located at gateways, the places where two or more networks connect. Routers use headers and forwarding tables to determine the best path for forwarding the packets, and they use protocols such as ICMP to communicate with each other and configure the best route between any two hosts.
In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) and sometimes the network layer (layer 3) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs. (2) A small lever or button. The switches on the back of printers and on expansion boards are called DIP switches. A switch that has just two positions is called a toggle switch. (3) Another word for option or parameter -- a symbol that you add to a command to modify the command's behavior. Very little filtering of data is done through routers.
A computer or device on a network that manages network resources. For example, a file server is a computer and storage device dedicated to storing files. Any user on the network can store files on the server. A print server is a computer that manages one or more printers, and a network server is a computer that manages network traffic. A database server is a computer system that processes database queries. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks.On multiprocessing operating systems, however, a single computer can execute several programs at once. A server in this case could refer to the program that is managing resources rather than the entire computer.
802.11g, is an amendment to the IEEE 802.11 specification that extended throughput to up to 54 Mbit/s using the same 2.4 GHz band. This specification under the marketing name of Wi-Fi has been implemented all over the world. The amendment has been incorporated into the published IEEE 802.11-2007 standard. 802.11 is a set of IEEE standards that govern wireless networking transmission methods. They are commonly used today in their 802.11a, 802.11b, and 802.11g versions to provide wireless connectivity in the home, office and some commercial establishments.
(1) Short for Domain Name System (or Service or Server), an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 198.105.232.4. The DNS system is, in fact, its own network. If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.
Analog signal processing is any signal processing conducted on analog signals by analog means. "Analog" indicates something that is mathematically represented as a set of continuous values. This differs from "digital" which uses a series of discrete quantities to represent signal. Analog values are typically represented as a voltage, electric current, or electric charge around components in the electronic devices. An error or noise affecting such physical quantities will result in a corresponding error in the signals represented by such physical quantities.
(American Standard Code for Information Interchange) A popular standard for writing letters and other characters in binary code. Originally, ASCII characters were seven bits, so there were 127 possible values. ASCII has been expanded to an 8-bit version, allowing 128 additional values.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Binary number
The smallest unit of data a computer can process, used in a binary system which is a number system used by computers that has just two unique digits,0 and 1, called bits.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Character
In computer software, any symbol that requires one byte of storage. This includes all the ASCII and extended ASCII characters, including the space character. In character-based software, everything that appears on the screen, including graphics symbols, is considered to be a character. In graphics-based applications, the term character is generally reserved for letters, numbers, and punctuation.
Or hexadecimal notation. A numbering system that uses 16 digits, the numerals 0-9, and the letters A-F. Hexadecimal notation is often used to display memory messages.
Dean, Tamara (2006). Network+ Guide to Networks, Fourth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thomson Learning, Inc..
Octet
One of the four 8-bit bytes that are separated by periods and together make up an IP address.
Andrews, Jean (2007). A+ Guide to Managing and Maintaining Your PC, Sixth Edition. Boston, Massachusetts: Thomson Course Technology, a division of Thompson Learning, Inc..
HTML
Short for HyperText Markup Language, the authoring language used to create documents on the World Wide Web. HTML is similar to SGML, although it is not a strict subset.
Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.
Short forStandard Generalized Markup Language, a system for organizing and tagging elements of a document. SGML was developed and standardized by the International Organization for Standards (ISO) in 1986. SGML itself does not specify any particular formatting; rather, it specifies the rules for tagging elements. These tags can then be interpreted to format elements in different ways.
Short for Extensible Hypertext Markup Language, a hybrid between HTML and XML specifically designed for Net device displays. XHTML is a markup language written in XML; therefore, it is an XML application. XHTML uses three XML namespaces (used to qualify element and attributes names by associating them with namespaces identified by URI references. Namespaces prevent identically custom-named tags that may be used in different XML documents from being read the same way), which correspond to three HTML 4.0 DTDs: Strict, Transitional, and Frameset. XHTML markup must conform to the markup standards defined in a HTML DTD. When applied to Net devices, XHTML must go through a modularization process. This enables XHTML pages to be read by many different platforms. A device designer, using standard building blocks, will specify which elements are supported. Content creators will then target these building blocks--or modules. Because these modules conform to certain standards, XHTML's extensibility ensures that layout and presentation stay true-to-form over any platform.
(1) Short for Cascading Style Sheets, a new feature being added to HTML that gives both Web site developers and users more control over how pages are displayed. With CSS, designers and users can create style sheets that define how different elements, such as headers and links, appear. These style sheets can then be applied to any Web page. The term cascading derives from the fact that multiple style sheets can be applied to the same Web page. CSS was developed by the W3C.
Computer files containing details of amendments to records, which may be used in the event of system recovery being required. The majority of commercial systems feature the creation of an audit log. Enabling this feature incurs some system overhead, but it does permit subsequent review of all system activity, and provide details of: which User ID performed which action to which files when etc. Failing to produce an audit log means that the activities on the system are 'lost'.
The process of identifying an individual, usually based on a username and password. In security systems, authentication is distinct from authorization , which is the process of giving individuals access to system objects based on their identity. Authentication merely ensures that the individual is who he or she claims to be, but says nothing about the access rights of the individual.
The degree to which a system, subsystem, or equipment is operable and in a committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time. Simply put, availability is the proportion of time a system is in a functioning condition.
The condition wherein the data transferred to a buffer exceeds the storage capacity of the buffer and some of the data “overflows” into another buffer, one that the data was not intended to go into. Since buffers can only hold a specific amount of data, when that capacity has been reached the data has to flow somewhere else, typically into another buffer, which can corrupt data that is already contained in that buffer. Malicious hackers can launch buffer overflow attacks wherein data with instructions to corrupt a system are purposely written into a file in full knowledge that the data will overflow a buffer and release the instructions into the computer’s instructions.
Confidentiality has been defined by the International Organization for Standardization (ISO) as "ensuring that information is accessible only to those authorized to have access" and is one of the cornerstones of Information security.
The translation of data into a secret code. Encryption is the most effective way to achieve data security. To read an encrypted file, you must have access to a secret key or password that enables you to decrypt it. Unencrypted data is called plain text ; encrypted data is referred to as cipher text. There are two main types of encryption: asymmetric encryption (also called public-key encryption) and symmetric encryption.
A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria. There are several types of firewall techniques: # Packet filter: Looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing. # Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation. # Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking. # Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses. In practice, many firewalls use two or more of these techniques in concert. A firewall is considered a first line of defense in protecting private information. For greater security, data can be encrypted.
Refers to the validity of data. Data integrity can be compromised in a number of ways: # Human errors when data is entered # Errors that occur when data is transmitted from one computer to another # Software bugs or viruses # Hardware malfunctions, such as disk crashes # Natural disasters, such as fires and floods There are many ways to minimize these threats to data integrity. These include: # Backing up data regularly # Controlling access to data via security mechanisms # Designing user interfaces that prevent the input of invalid data # Using error detection and correction software when transmitting data
Programming code added to the software of an application or operating system that lies dormant until a predetermined period of time (i.e., a period of latency) or event occurs, triggering the code into action. Logic bombs typically are malicious in intent, acting in the same ways as a virus or Trojan horse once activated. In fact, viruses that are set to be released at a certain time are considered logic bombs. They can perform such actions as reformatting a hard drive and/or deleting, altering or corrupting data.
Abbreviated as PGP, a technique developed by Philip Zimmerman for encrypting messages. PGP is one of the most common ways to protect messages on the Internet because it is effective, easy to use, and free. PGP is based on the public-key method, which uses two keys -- one is a public key that you disseminate to anyone from whom you want to receive a message. The other is a private key that you use to decrypt messages that you receive. To encrypt a message using PGP, you need the PGP encryption package, which is available for free from a number of sources. The official repository is at the Massachusetts Institute of Technology. PGP is such an effective encryption tool that the U.S. government actually brought a lawsuit against Zimmerman for putting it in the public domain and hence making it available to enemies of the U.S. After a public outcry, the U.S. lawsuit was dropped, but it is still illegal to use PGP in many other countries.
The act of sending an e-mail to a user falsely claiming to be an established legitimate enterprise in an attempt to scam the user into surrendering private information that will be used for identity theft. The e-mail directs the user to visit a Web site where they are asked to update personal information, such as passwords and credit card, social security, and bank account numbers, that the legitimate organization already has. The Web site, however, is bogus and set up only to steal the user’s information.
Short for public key infrastructure, a system of digital certificates, Certificate Authorities, and other registration authorities that verify and authenticate the validity of each party involved in an Internet transaction. PKIs are currently evolving and there is no single PKI nor even a single agreed-upon standard for setting up a PKI. However, nearly everyone agrees that reliable PKIs are necessary before electronic commerce can become widespread.
In the realm of computers, the act of obtaining or attempting to obtain otherwise secure data by conning an individual into revealing secure information. Social engineering is successful because its victims innately want to trust other people and are naturally helpful. The victims of social engineering are tricked into releasing information that they do not realize will be used to attack a computer network.
Electronic junk mail or junk newsgroup postings. Some people define spam even more generally as any unsolicited e-mail. However, if a long-lost brother finds your e-mail address and sends you a message, this could hardly be called spam, even though it's unsolicited. Real spam is generally e-mail advertising for some product sent to a mailing list or newsgroup. In addition to wasting people's time with unwanted e-mail, spam also eats up a lot of network bandwidth. Consequently, there are many organizations, as well as individuals, who have taken it upon themselves to fight spam with a variety of techniques. But because the Internet is public, there is really little that can be done to prevent spam, just as it is impossible to prevent junk mail. However, some online services have instituted policies to prevent spammers from spamming their subscribers. There is some debate about the source of the term, but the generally accepted version is that it comes from the Monty Python song, "Spam spam spam spam, spam spam spam spam, lovely spam, wonderful spam…" Like the song, spam is an endless repetition of worthless text. Another school of thought maintains that it comes from the computer group lab at the University of Southern California who gave it the name because it has many of the same characteristics as the lunchmeat Spam: * Nobody wants it or ever asks for it. * No one ever eats it; it is the first item to be pushed to the side when eating the entree. * Sometimes it is actually tasty, like 1% of junk mail that is really useful to some people.
A password that is difficult to detect by both humans and computer programs, effectively protecting data from unauthorized access. A strong password consists of at least six characters (and the more characters, the stronger the password) that are a combination of letters, numbers and symbols (@, #, $, %, etc.) if allowed. Passwords are typically case-sensitive, so a strong password contains letters in both uppercase and lowercase. Strong passwords also do not contain words that can be found in a dictionary or parts of the user’s own name.
A program or piece of code that is loaded onto your computer without your knowledge and runs against your wishes. Viruses can also replicate themselves. All computer viruses are manmade. A simple virus that can make a copy of itself over and over again is relatively easy to produce. Even such a simple virus is dangerous because it will quickly use all available memory and bring the system to a halt. An even more dangerous type of virus is one capable of transmitting itself across networks and bypassing security systems.
Short for virtual private network, a network that is constructed by using public wires to connect nodes. For example, there are a number of systems that enable you to create networks using the Internet as the medium for transporting data. These systems use encryption and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted.
A program or algorithm that replicates itself over a computer network and usually performs malicious actions, such as using up the computer's resources and possibly shutting the system down.
The ampersand (&) normally means "and" as in Jones & Company. However, in the computer world, it is used in various ways. In Windows, it is used as a code to precede an underlined character. As a result, in some input dialogs, you have to enter a double ampersand (&&) to actually define a single ampersand. In programming, a double ampersand is used to represent the Boolean AND operator such as in the C statement, if (x >= 100 && x >= 199). In HTML, the ampersand is used as a prefix to a mnemonic name, followed by a semicolon, for foreign letters and special characters such as the copyright and trademark symbols. When an HTML tag must be described on an HTML page rather than rendered as actual HTML, the ampersand precedes lt (less than) or gt (greater than), followed by a semicolon.
The at sign (@), which is shorthand for the word "at," has become widely identified around the world due to its use in Internet e-mail addresses. Officially known as an "asperand," the at sign separates the recipient's name from the domain name; for example, jsmith@abc.com. In 1971, Ray Tomlinson of Bolt Beranek and Newman chose the @ sign as a separator symbol for one of the first e-mail systems.
The backslash symbol (\) is used as a separator between folder and file names in DOS, Windows and OS/2 when the full path to a file is written out. For example, the path c:\cde\cde.exe points to the CDE.EXE file in the CDE folder on the C: drive. When the universal naming convention (UNC) is used, double backslash (\\) characters serve as a prefix to the server name (see UNC). In DOS and Windows programming, double backslash characters (\\) represent an actual single backslash that will be displayed or printed. This is required since the symbol is used to separate names and also define hexadecimal numbers.
The forward slash, or slash, character (/) is the divide symbol in programming and on calculator keyboards. For example, 10 / 7 means 10 divided by 7. The slash is also often used in command line syntax to indicate a switch. For example, in the DOS Xcopy statement xcopy *.* d: /s, the /s is a switch that tells the program to copy all subdirectories. In Unix paths, which have become popular due to Internet addresses, the slash separates the elements of the path as in www.company.com/news/previous/abc.html. See backslash.
In typography, italic refers to fonts with characters slanted to the right. An italic font, however, often includes one or more character shapes, such as the a and the f, that differ from those in the roman font of the same family.
Refers to fonts in which each character has the same width. The opposite of monospacing is proportional spacing, in which different characters have different widths. For example, in a proportionally spaced font, the letter o would be wider than the letter i. Proportionally spaced fonts look more professional, but monospaced fonts are often superior for tabular data because the uniform width of each character makes alignment of columns easier.
In typography, a point is about 1/72 of an inch and is used to measure the height of characters. (Historically, a point was.0138 inches, a little less than 1/72 of an inch, but this has changed.) The height of the characters is one characteristic of fonts. Some fonts are referred to as fixed-point fonts because their representation allows for only one size. In contrast, a scalable font is one that is represented in such a way that the size can easily be changed.
Pronounced SAN-SERR-if. A category of typefaces that do not use serifs, small lines at the ends of characters. Popular sans serif fonts include Helvetica, Avant Garde, Arial, and Geneva.
A small decorative line added as embellishment to the basic form of a character. Typefaces are often described as being serif or sans serif (without serifs). The most common serif typeface is Times Roman.
A symbol used in Windows, starting with Windows 95, that maintains a short version of a long file or directory name for compatibility with Windows 3.1 and DOS. For example, the short version of a file named "Letter to Joe" would be LETTER~1. Then "Letter to Pat" becomes LETTER~2. In the Unix world, all the popular Unix shells (except for the Bourne shell) support a home directory name substitution using the tilde. Also called a "squiggle" or "twiddle," the symbol is used as a prefix to a user login name to specify that user's home directory. For example, if your user name were "jackson," you would use ~jackson to refer to your home directory.
GROUP 11 TERMINOLGY PAGE
Hardware/Software Terms
Markup Terms
Networking/Communication Technology Terms
Language/Coding Terms
Security Terms
Formatting Terms